External Radiation

The specific gamma ray constant for Tc 99m is 0.78 R/ hour-millicurie at 1 cm. The first half-value layer is 0.017 cm lead (Pb). A range of values for the relative attenuation of the radiation emitted by this radionuclide that results from interposition of various thicknesses of Pb is shown in Table 2. To facilitate control of the radiation exposure from millicurie amounts of this radionuclide, the use of a 0.25 cm thickness of Pb will attenuate the radiation emitted by a factor of about 1,000.

To correct for physical decay of technetium Tc 99m, the fractions that remain at selected intervals after the time of calibration are shown in Table 3.

General

The contents of the kit before preparation are not radioactive. However, after the sodium pertechnetate Tc 99m injection is added, adequate shielding of the final preparation must be maintained.

Contents of the reaction vial are intended only for use in the preparation of technetium Tc 99m medronate and are NOT to be administered directly to the patient.

Technetium Tc 99m medronate as well as other radioactive drugs, must be handled with care. Once sodium pertechnetate Tc 99m is added to the vial, appropriate safety measures should be used to minimize external radiation to clinical occupational personnel. Care should also be taken to minimize radiation exposure to patients in a manner consistent with proper patient management.

To minimize the radiation dose to the bladder, the patient should be encouraged to drink fluids and to void immediately before the examination and as often thereafter as possible for the next four to six hours.

Technetium Tc 99m medronate should be formulated within six (6) hours prior to clinical use. Optimal imaging results are obtained one to four hours after administration. Technetium Tc 99m medronate injection should be discarded six hours after reconstitution. The solution should not be used if cloudy.

The components of the kit are sterile and pyrogen-free. It is essential to follow directions carefully and to adhere to strict aseptic procedures during preparation.

The technetium Tc 99m labeling reactions involved in preparing the agent depend on maintaining the stannous ion in the reduced state. Any oxidant present in the sodium pertechnetate Tc 99m supply may, thus, adversely affect the quality of the radiopharmaceutical. Hence, sodium pertechnetate Tc 99m containing oxidants should not be employed.

Radiopharmaceuticals should be used only by physicians who are qualified by training and experience in the safe use and handling of radionuclides.

Carcinogenesis, Mutagenesis, Impairment of Fertility

No long-term animal studies have been performed to evaluate carcinogenic potential or whether technetium Tc 99m medronate affects fertility in males or females.

Pregnancy

Pregnancy Category C

Animal reproduction studies have not been conducted with technetium Tc 99m medronate. It is also not known whether technetium Tc 99m medronate can cause fetal harm when administered to a pregnant woman or can affect reproductive capacity. Technetium Tc 99m medronate should be given to a pregnant woman only if clearly needed.

Nursing Mothers

Technetium Tc 99m is excreted in human milk during lactation; therefore, formula-feedings should be substituted for breast-feedings.

Pediatric Use

Safety and effectiveness in children have not been established.

Radiation Dosimetry

The effective half-life was assumed to be the physical half-life for all calculated values. The estimated radiation absorbed doses to an average patient (70 kg) from an intravenous injection of a maximum dose of 740 megabecquerels (20 millicuries) of technetium Tc 99m medronate are shown in Table 4.

Method of Calculation: “S” Absorbed Dose per Unit Cumulated Activity for Selected Radionuclides and Organs, MlRD Pamphlet No. 11, 1975

Storage

Store the product as supplied at 20-25°C (68-77°F) [See USP]. After reconstitution store refrigerated at 2-8°C (36-46°F) (see DOSAGE AND ADMINISTRATION).

Procedural Precautions

The lyophilized powder in the reaction vial is sterile and nonpyrogenic and does not contain a preservative. Aseptic procedure and shielded syringes should be used when adding the pertechnetate eluate to the reaction vial and for withdrawal and administration of the dose of the finished medronate agent. Waterproof gloves should be worn to prevent the possibility of radioactive contamination of the hands.

If sodium pertechnetate Tc 99m must be diluted prior to injection into the reaction vial, only Sodium Chloride Injection USP 0.9% (without preservatives) should be used.

Preparation

Preparation of technetium Tc 99m medronate is done by the following aseptic procedure:

1. Waterproof gloves should be worn during the preparation procedure.
2. Place reaction vial in an appropriate lead shield.
3. Remove the central disc from the reaction vial and swab the rubber closure of the reaction vial with a germicide.
4. With a sterile syringe, aseptically obtain 0.5 to 5 mL, [up to 18.5 gigabecquerels (500 millicuries)] of a suitable, oxidant-free, sterile nonpyrogenic sodium pertechnetate.
5. Aseptically add the sodium pertechnetate Tc 99m solution to the vial.
6. Secure the lead shield cover. Swirl the vial for one minute and let stand for one to two minutes.
7. Record the date and time of preparation on pressure-sensitive label.
8. Affix pressure-sensitive label to shield.
9. Examine vial contents. If the solution is not clear and free of particulate matter and discoloration on visual inspection, it should not be used.
10. Measure the radioactivity using a suitable calibration system and record on the shield label prior to patient administration.
11. Aseptically withdraw material for use within six (6) hours of preparation. For optimum results, this time should be minimized.The vial contains no bacteriostatic preservative.